Hawai'i's Environment
Intruders threaten Hawai'i waters

By Jan TenBruggencate
Advertiser Staff Writer

The Pew Oceans Commission, which is looking into threats facing the marine world, has issued a report calling introduced species one of the major threats to nearshore environments, in Hawai'i and elsewhere.

"Introduced species of crabs, mussels, clams, jellyfish, seagrasses and marsh grasses dominate marine ecosystems from the Hawaiian Islands" across the coastal areas of the nation, says the report, "Introduced Species in U.S. Coastal Waters."

Author James Carlton of Williams College and Mystic Seaport calls the continual arrival of new species on coastlines a "game of ecological roulette."

In the Islands, we have seen a range of marine intruders take hold through various means.

There are seaweeds introduced for research purposes and fish, such as the blue-line snapper or taape, which were released on purpose to improve fishery diversity and became dominant species, pushing out native marine life.

Seaweeds arrive on the bottoms of ships and immediately colonize other boats, reefs and piers. Organisms that travel from foreign ports in the bilge water of ships are pumped into our waters, where they spread as unwanted immigrants.

Hawai'i is better known for its problem with land-based intruders, like the invasive plant miconia, disease-bearing mosquitoes, and feral pigs in the forests. But our waters are not protected from similar problems.

"More than 100 introduced species now occur in Pearl Harbor alone," Carlton wrote.

"The intentionally introduced Philippine seaweed (Kappaphycus alvarezii and Kappaphycus striatum) covers large areas of Kane'ohe Bay coral reefs, reducing potential tourist value. The red mangrove, (Rhizophora mangle) —which was introduced intentionally — now occupies more than 70 percent of O'ahu's estuarine shores," he wrote.

In another introduction, when the USS Missouri was towed from Puget Sound to Pearl Harbor, it had Mediterranean mussels on its hull. Later, the mussels appeared in the ballast tanks of a submarine moored nearby. While the Missouri had been towed into the fresh water of the Columbia River to kill off marine organisms, apparently the deep bottom of the hull remained in salt water at the river bottom, allowing the mussels to survive.

It is extremely difficult to control a bioinvader once it's established. Carlton said the best approach is to prevent their arrival through mandatory management of ballast water and ship bottoms, and to have a rapid-response program for controlling new invaders before they're fully established.

There are no formal regulatory tools in place to prevent or control new introductions of most kinds of invaders, Carlton said.

Jan TenBruggencate is The Advertiser's Kaua'i bureau chief and its science and environment writer. You can call him at 245-3074 or e-mail jant@honoluluadvertiser.com.